This invention relates to automated bulk inspection and processing systems and, in particular, to multi-band optical inspection and sorting of light-weight articles, such as stripped-leaf tobacco or laminae, tobacco stems, and reclaimed tobacco.
Automated bulk optical processing equipment can perform a variety of tasks such as, for example, inspecting or sorting bulk articles including raw or processed fruit, vegetables, wood chips, recycled plastics, and other similar products. The articles may be classified according to size, color, shape, or other qualities. Modern bulk optical processing equipment can rapidly classify and separate very large quantities of such articles into numerous categories.
Such equipment typically includes a conveyor system for moving the articles past an inspection station where cameras or other detection devices examine the articles as they pass through an inspection zone. The inspection station sends signals to a sorting or treatment station where the articles are sorted or otherwise treated by category. For example, defective or foreign articles may be removed from the flow of articles carried by the conveyor system.
Rapid inspection or sorting of large quantities of articles typically requires high-speed conveyor systems such as, for example, conveyor belts with widths of two to six feet (0.6 to 1.8 meters) that convey the articles at speeds of over 17 feet per second (5 meters per second). A problem conveying articles at such speeds is that light-weight articles are relatively unstable and tend to roll, tumble, bounce, and collide with one another. Unstable articles carried by a high-speed conveyor system are difficult to inspect, sort or otherwise process for at least two reasons.
First, automated bulk optical processing equipment includes cameras or other optical detectors that optically determine selected characteristics of the articles (e.g., size, color, and shape). The rolling, tumbling or bouncing of an article typically diminishes the clarity with which an image of the article is generated, thereby decreasing the accuracy and reliability of the optical information about the article. As extreme examples, rolling could cause a cubic article to appear round, or an article with differently colored regions could appear to have a single mixed color.
Second, unstable articles can move laterally and/or longitudinally relative to direction of conveyor belt travel. Lateral article movement is undesirable because it misaligns the articles as they pass from the inspection station to the processing station, thereby resulting in incorrect processing. Similarly, longitudinal article movement along the direction of belt travel causes effective speed differences that place the articles in temporal misalignment for subsequent processing operations.
Some articles have increased susceptibility to unstable motion on a conveyor, such as light-weight articles and articles of low and non-uniform density. Particular examples of such articles include stripped-leaf tobacco or laminae, tobacco stems, and reclaimed tobacco. Other examples include undesirable debris such as, for example, feathers, paper, cardboard, plastic, string, rope, dirt, twigs, stones, insects, animal parts, and rubber that may incidentally be included within the acceptable articles. As a consequence, these types of articles are difficult to inspect and sort accurately at high speeds.
One attempt to solve such instability problems can be seen in U.S. Pat. No. 5,297,667 for A SYSTEM FOR STABILIZING ARTICLES ON CONVEYORS, which assigned to the assignee of this patent application. This device uses a hood located just above the belt to create a flow of gas (e.g., air) projected along the conveyor belt in a direction generally parallel to that in which the articles are carried by the belt. The air flow has a velocity substantially the same as that above the belt to reduce aerodynamic resistance that would otherwise bear against the articles causing them to become unstable. Since this resistance is reduced, the articles carried by the belt are relatively stable. The articles are accelerated by and propelled from the belt in-air along a known and predictable trajectory to a sorting or processing station. The successful operation of the sorter or processor depends on the products being propelled along the known trajectory. Thus, the processor notes the exact position of the articles as they pass by and can separate defective or undesirable articles from the volume of acceptable articles. This type of system has been successful for articles having a relatively high mass. Articles with high mass are able to maintain their velocity in-air as they are projected from the belt and continue along their predicted trajectory.
Another attempt to stabilize articles as they are moved along a conveyor belt is the use of a second counter-rotating conveyor belt located above and close to the conveyor belt on which the articles are positioned. Instead of blowing air through a hood that encloses the conveyor belt, the second counter-rotating conveyor belt creates a flow of air in a direction generally parallel to the direction of travel of the articles. The flow of air generated by the second counter-rotating conveyor belt has a velocity about the same as the article-conveying belt to reduce any aerodynamic resistance that would otherwise bear against the articles. One example of such a system is the Tobacco Scan 6000 manufactured by Elbicon located near Brussels, Belgium.
However, these systems are inadequate for very light articles such as the above-described tobacco products and light-weight debris or articles weighing about 1.5 to five pounds per cubic foot. Light-weight articles become unstable after they leave the belt and travel along an unknown trajectory. This happens because air flow becomes unstable after it leaves the belt. The air profile separates into a random flow pattern. A portion of the air flows downward while another portion flows straight. Yet other parts of the air may flow upward or in a direction transverse to the direction of travel of the belt. The light-weight articles do not have enough mass to continue along a predicted trajectory. They lose velocity and are drawn into a random air flow pattern. The positions of the articles cannot be predicted at a specific time. This makes accurate processing of the articles difficult and impractical.
Another problem with existing systems is inadequate illumination, detection, and sorting of the articles and, in particular, tobacco products that may include black butyl rubber particles, tobacco-stained latex rubber glove debris, brown cardboard, red cardboard, green paper, and blue plastic rope. The black butyl rubber particles may be contaminants from the rubber-wrapped piping systems that transport cooling water in tobacco processing facilities, or they may be intentionally added to the particle flow to test the inspection and sorting capabilities of the system. The tobacco-stained latex rubber glove debris contaminates the tobacco products as a result of handling by latex-gloved human laborers. Unfortunately, because these particular rubber particles are so visibly similar to tobacco products, that are difficult to detect with present inspection systems. The other contaminants are bits and pieces of containers and packaging employed in transporting and storing the tobacco products. Because of their colors, conventional sorting techniques render some of them difficult to distinguish from the good tobacco products.
What is needed, therefore, is a suitable conveyor for light-weight articles, such as tobacco products, combined with an inspection system that can detect and classify tobacco products containing butyl, latex, and other debris
An object of this invention is, therefore, to provide an improved conveyor for use with automated bulk processing equipment.
Another object of this invention is to increase stability of light-weight articles as they are carried on and projected in-air from such conveyors.
A further object of this invention is to provide such a conveyor that is capable of allowing increased accuracy in optical processing of light-weight articles and articles of low and non-uniform density.
Still another object of the invention is to provide a system with multi-spectral illumination and sorting of the articles and, in particular tobacco products.
An off-belt stabilizing system of this invention stabilizes light-weight articles as they are projected in-air from a conveyor belt for automated bulk processing equipment. In a preferred embodiment, the light-weight articles are stabilized along a conveyor belt from a first infeed end to a second discharge end. The off-belt stabilizing system provides a totally enclosed system that stabilizes the light-weight articles as they are projected in-air from the second discharge end of the conveyor belt. The air flow at and past the end of the belt is controlled by a hood structure so that light-weight articles that are projected within the air flow travel along a known and predictable trajectory.
This invention also includes improved multi-spectral illumination and sensing of the articles, which is achieved by incorporating a pair of oppositely facing optical illuminating stations and a sorting station into the off-belt stabilizing system. Windows are provided in upper and lower surfaces of the hood structure through which the illumination stations provide red (xe2x80x9cRxe2x80x9d), green (xe2x80x9cGxe2x80x9d), and infrared (xe2x80x9cIRxe2x80x9d) illumination (or other wavelength combinations) of both major surfaces of the articles as they pass by an associated pair of line-scanning xe2x80x9ccolorxe2x80x9d cameras. Dichroic prisms render the cameras sensitive to the R, G, and IR wavelengths of the illumination stations. The windows extend between the illumination stations and the articles as they travel in-air through the stabilizing system and along their trajectory.
R, G, and IR illumination provides sufficiently differing ratios of reflected R, G, and IR radiation that are usable for making reliable article classification sorting decisions for the above-described tobacco and other products.